Impacts of Forest Fire on Boreal Lakes
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![Page 1: Impacts of Forest Fire on Boreal Lakes](https://reader035.fdocuments.us/reader035/viewer/2022062721/56813827550346895d9fd4c6/html5/thumbnails/1.jpg)
Impacts of Forest Fire on Boreal Lakes
Tess ChadilSource: http://blog.e-democracy.org/posts/91
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Impacts to Physical
Watershed Processes
Source: http://www.wrh.noaa.gov/wrh/02TAs/0212/figure23.gif
http://wwwbrr.cr.usgs.gov/projects/Burned_Watersheds/Rll_IntR.jpg
Devegetation Hydrophobic Soils
↓interception↓ transpiration
↑ runoff
↑ erosion
↑ sediment transport
↑ion and nutrient contributions to lakes
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Ion and Nutrient Transport
• Magnitude of flux into lake depends on– Severity of fire– Depth of organic layer in soil
• P and N transport have most significant impacts to lake water quality
• Fire leads to increased concentrations of K+, Ca2+, Mg2+, Cl-, SO4
2-
• Local deposition of particulate Hg
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Phosphorous and Nitrogen• Significant increases in total, total dissolved
and soluble reactive phosphorous– 74% of variance in TP can be explained by percent
of basin burned, and time elapsed since fire– Most boreal lakes are naturally P-limited
• Significant increases in total and total dissolved nitrogen, nitrates and ammonium– Primary source for nitrates is ash– Persistent nitrate contamination sustained by
contaminated groundwater inflows
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Additional Effects of Fire• Increased concentration of inorganic suspended
solids– Mean light extinction nearly doubled in some cases
• No significant increases to DOC• Increases in pH varied among studies
– some lakes experience permanent increases in pH
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Aquatic Ecology
• Boreal lakes in burned watersheds tend towards eutrophy– Lakes in burned watersheds reported TP:TN ratios between 10 and 20– Cyanobacteria blooms lead to diminished water quality– Reduced clarity helps to limit chlorophyll-a concentrations
Source: http://biology.mcgill.ca/grad/alison/photos/researchInterest1.jpg
• Reduced algal species richness•Increased Hg concentrations reported in fish
•Hg concentrations limited by “growth-dilution” effect
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Recovery Rate• Recovery rate
dependent on:– Ratio of burned
watershed area to lake surface area
– Predominant vegetation
•Recovery to pre-burn conditions takes decades
•Most studies are short-term (less than 10 years), or•Paleolimnological Investigations (100s or 1000s of years)
Source: http://barbagallo.files.wordpress.com/2009/09/img_4721.jpg
Source: http://interwork.sdsu.edu/fire/resources/images/MiddlePeak2.jpg
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Paleolimnology
Source: http://www.scielo.br/img/revistas/bn/v6n1/a01f06.gif
Source: http://www.pc.gc.ca/eng/pn-np/bc/kootenay/natcul/natcul23.aspx
Source: http://post.queensu.ca/~low/Research%20Page.html
Source: http://www.biol.canterbury.ac.nz/ferg/Images/Sediment-core-lake-Rotorua-(Kaikoura)-lg.jpg
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Management Implications• Climate change – Increased incidence
of fire– Increased nutrient
transport potential
• Fire Management Practices
• Fisheries value• Need for further
long-term studiesSource: http://www.ec.gc.ca/INRE-NWRI/0CD66675-AD25-4B23-892C-5396F7876F65/ch8-forestfire%5B1%5D.jpg